/Engine/Source/Runtime/SlateCore/Public/Widgets/SBoxPanel.h
Drag detection and handling
virtual [FReply](API\Runtime\SlateCore\Input\FReply) OnMouseButtonDown ( const [FGeometry](API\Runtime\SlateCore\Layout\FGeometry) & MyGeometry, const [FPointerEvent](API\Runtime\SlateCore\Input\FPointerEvent) & MouseEvent )